182 Domestic Science 



10. By how much will the temperature of a litre of ice-cold 

 water be raised by the condensation of 100 g. of steam in it? 



11. Why is it advantageous to put some salt in the water with 

 which doorsteps are cleaned in frosty weather ? 



12. How many calories must be supplied to melt a block of 

 ice which measures 25 cm. X 15 cm. X 10'8 cm. ? 



13. Describe fully an experiment in which it is shown that the 

 liquefaction of a solid is attended by absorption of heat, and another 

 in which the solidification of a liquid is shown to cause the evolution 

 of heat. 



14. A stout glass bottle is completely filled with water and 

 securely stoppered. It is then placed in the open air on a day when 

 the thermometer registers 23 F. Describe what you would expect 

 to happen. 



15. A lump of ice is thrown into a vessel containing a quantity 

 of alcohol at 25 C. What happens ? 



16. Suggest two reasons for tea being cooled by dissolving sugar 

 in it. 



17. Of what advantage to mankind is the fact that water gives 

 out heat while freezing ? 



18. Most substances occupy a greater volume when in the liquid 

 state than when solid. What useful purpose is served in nature by 

 the peculiar behaviour of water in this respect ? 



CHAPTER XI 



THE PROPAGATION OF HEAT 



119. In the preceding chapters on heat we have 

 frequently spoken of heat being transmitted from one 

 body to another, and the experiments performed have 

 afforded evidence that this transmission actually takes 

 place. We will next take up the question of the 

 various methods by which heat moves from one body to 

 another, or from one part of a body to some other part. 



